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Papers by Evgeny Wasserman
Physical Review B, 1996
We investigate the thermoelastic properties of close-packed phases of iron at pressures up to 400... more We investigate the thermoelastic properties of close-packed phases of iron at pressures up to 400 GPa and temperature to 6000 K using a tight-binding total-energy method and the cell model of the vibrational partition function. The calculated properties are in good agreement with available static and shock-wave experimental measurements. The compressional behavior of a number of thermoelastic parameters is found to resemble that of a prototypical oxide ͑MgO͒ supporting some aspects of universal behavior at high compression: the product of thermal expansivity ␣ and bulk modulus is found to be nearly independent of compression at high pressure and the logarithmic volume derivative of ␣ is found to decrease with compression. In contrast to the behavior of MgO, ␣K T and ␦ T of iron are found to depend strongly on temperature due to contributions from the thermal excitation of electrons. Significant decrease of the elastic constants of hcp iron with temperature was found.
MRS Proceedings, 1997
ABSTRACTWe have further developed and applied a new non-empirical tight-binding total energy mode... more ABSTRACTWe have further developed and applied a new non-empirical tight-binding total energy model to properties of Si, Xe, and Fe at high pressures. We have studied elasticity of various phases of each of these, demonstrating that the new model is applicable to a wide range of materials, including semiconductors, rare gases, and transition metals. We have used the particle-in-a-cell method to study the thermal equation of state of hep Fe and find excellent agreement with the shock equation of state. A molecular dynamics code has been developed based on this method, and we have studied the properties of Fe liquid at high pressures.
Journal of Geophysical Research: Solid Earth, 1997
Page 1. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 102, NO. Bll, PAGES 24,729-24,739 NOVEMBER 10, 1997... more Page 1. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 102, NO. Bll, PAGES 24,729-24,739 NOVEMBER 10, 1997 Composition and temperature of Earth's inner core Lars Stixrude1 and Evgeny Wasserman2 Department ...
Applied and Environmental Microbiology, 1998
A methodology is presented for calculating of the surface potential, Donnan potential, and ion co... more A methodology is presented for calculating of the surface potential, Donnan potential, and ion concentration profiles for semipermeable microbial membranes that is valid for an arbitrary electrolyte composition. This model for surface potential, Donnan potential, and charge density was applied to recently reported experimental data for gram-positive bacteria, including Bacillus brevis , Rhodococcus opacus , Rhodococcus erythropolis , and Corynebacterium species. These calculations show that previously unconsidered trace amounts of divalent and trivalent cations at very low concentrations (10 −6 M) can have significant effects on the calculated surface and Donnan potentials, at ionic strengths of I ≤ 0.01 M, and that these effects need to be considered in accurate modeling of microbial surface. In addition, the calculated ion concentration profiles show that owing to the relatively high surface charges that can develop in microbial membranes, electrostatic effects can act to signific...
Geochimica et cosmochimica acta, 1995
The static dielectric constant of water was calculated by molecular dynamics simulations using th... more The static dielectric constant of water was calculated by molecular dynamics simulations using the SPC/E water model up to 1273 K and pressures to 20 kbar. Simulations within the pressure-temperature range (up to 5 kbar and 823 K) of the available experimental data ...
Surface Science, 1997
We present a clear and rigorous derivation of the Ewald-like method for calculation of the electr... more We present a clear and rigorous derivation of the Ewald-like method for calculation of the electrostatic energy of the systems infinitely periodic in two-dimensions and of finite size in the third dimension (slabs). We have generalized this method originally developed by Rhee et al. [Phys. Rev. B 40, 36(1989)] to account for charge-dipole and dipole-dipole interactions and therefore made it suitable for treatment of polarizable systems. This method has the advantage over exact methods of being significantly faster and therefore appropriate for large-scale molecular dynamics simulations. It however involves a Taylor expansion which has to be demonstrated to be of sufficient order. The method was extensively benchmarked against the exact methods by Leckner and Parry. We found it necessary to increase the order of the multipole expansion from 4 (as in original work by Rhee et al.) to 6. In this case the method is adequate for aspect ratios (thickness/shortest side length of the unit cell) ≤ 0.5. Molecular dynamics simulations using the transferable/polarizable model by Rustad et al. were applied to study the surface relaxation of the nonhydroxylated, hydroxylated, and solvated surfaces of α-Fe2O3 (hematite). We find that our nonhydroxylated structures and energies are in good agreement with previous LDA calculations on α-alumina by Manassidis et al. [Surf. Sci. Lett. 285, L517, 1993]. Using the results of molecular dynamics simulations of solvated interfaces, we define end-member hydroxylated-hydrated states for the surfaces which are used in energy minimization calculations. We find that hydration has a small effect on the surface structure, but that hydroxylation has a significant effect. Our calculations, both for gas-phase and solutionphase adsorption, predict a greater amount of hydroxylation for the α-Fe2O3 (012) surface than for the (001) surface. Our simulations also indicate the presence of four-fold coordinated iron ions on the (001) surface.
A tight-binding total-energy model parametrized to first-principles linearized augmented plane-wa... more A tight-binding total-energy model parametrized to first-principles linearized augmented plane-wave computations is applied to study elasticity and elastic anisotropy in Fe, Xe, and Si at high pressures. We find that the model works well in reproducing the compression, electronic structure, phase relations, and elasticity in these diverse materials. In Xe, for example, the same parametrization works well over a fivefold compression range from a van der Waals solid to a dense metal. We find that the cubic close-packed structures are all more anisotropic than hexagonal close packed and that at high pressures the elastic anisotropy approaches that of any central force nearest-neighbor model. We find that long-range, nonorthogonal parametrizations are necessary for greatest accuracy. ͓S0163-1829͑97͒04738-3͔
Physical Review B, 1996
We investigate the thermoelastic properties of close-packed phases of iron at pressures up to 400... more We investigate the thermoelastic properties of close-packed phases of iron at pressures up to 400 GPa and temperature to 6000 K using a tight-binding total-energy method and the cell model of the vibrational partition function. The calculated properties are in good agreement with available static and shock-wave experimental measurements. The compressional behavior of a number of thermoelastic parameters is found to resemble that of a prototypical oxide ͑MgO͒ supporting some aspects of universal behavior at high compression: the product of thermal expansivity ␣ and bulk modulus is found to be nearly independent of compression at high pressure and the logarithmic volume derivative of ␣ is found to decrease with compression. In contrast to the behavior of MgO, ␣K T and ␦ T of iron are found to depend strongly on temperature due to contributions from the thermal excitation of electrons. Significant decrease of the elastic constants of hcp iron with temperature was found.
MRS Proceedings, 1997
ABSTRACTWe have further developed and applied a new non-empirical tight-binding total energy mode... more ABSTRACTWe have further developed and applied a new non-empirical tight-binding total energy model to properties of Si, Xe, and Fe at high pressures. We have studied elasticity of various phases of each of these, demonstrating that the new model is applicable to a wide range of materials, including semiconductors, rare gases, and transition metals. We have used the particle-in-a-cell method to study the thermal equation of state of hep Fe and find excellent agreement with the shock equation of state. A molecular dynamics code has been developed based on this method, and we have studied the properties of Fe liquid at high pressures.
Journal of Geophysical Research: Solid Earth, 1997
Page 1. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 102, NO. Bll, PAGES 24,729-24,739 NOVEMBER 10, 1997... more Page 1. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 102, NO. Bll, PAGES 24,729-24,739 NOVEMBER 10, 1997 Composition and temperature of Earth's inner core Lars Stixrude1 and Evgeny Wasserman2 Department ...
Applied and Environmental Microbiology, 1998
A methodology is presented for calculating of the surface potential, Donnan potential, and ion co... more A methodology is presented for calculating of the surface potential, Donnan potential, and ion concentration profiles for semipermeable microbial membranes that is valid for an arbitrary electrolyte composition. This model for surface potential, Donnan potential, and charge density was applied to recently reported experimental data for gram-positive bacteria, including Bacillus brevis , Rhodococcus opacus , Rhodococcus erythropolis , and Corynebacterium species. These calculations show that previously unconsidered trace amounts of divalent and trivalent cations at very low concentrations (10 −6 M) can have significant effects on the calculated surface and Donnan potentials, at ionic strengths of I ≤ 0.01 M, and that these effects need to be considered in accurate modeling of microbial surface. In addition, the calculated ion concentration profiles show that owing to the relatively high surface charges that can develop in microbial membranes, electrostatic effects can act to signific...
Geochimica et cosmochimica acta, 1995
The static dielectric constant of water was calculated by molecular dynamics simulations using th... more The static dielectric constant of water was calculated by molecular dynamics simulations using the SPC/E water model up to 1273 K and pressures to 20 kbar. Simulations within the pressure-temperature range (up to 5 kbar and 823 K) of the available experimental data ...
Surface Science, 1997
We present a clear and rigorous derivation of the Ewald-like method for calculation of the electr... more We present a clear and rigorous derivation of the Ewald-like method for calculation of the electrostatic energy of the systems infinitely periodic in two-dimensions and of finite size in the third dimension (slabs). We have generalized this method originally developed by Rhee et al. [Phys. Rev. B 40, 36(1989)] to account for charge-dipole and dipole-dipole interactions and therefore made it suitable for treatment of polarizable systems. This method has the advantage over exact methods of being significantly faster and therefore appropriate for large-scale molecular dynamics simulations. It however involves a Taylor expansion which has to be demonstrated to be of sufficient order. The method was extensively benchmarked against the exact methods by Leckner and Parry. We found it necessary to increase the order of the multipole expansion from 4 (as in original work by Rhee et al.) to 6. In this case the method is adequate for aspect ratios (thickness/shortest side length of the unit cell) ≤ 0.5. Molecular dynamics simulations using the transferable/polarizable model by Rustad et al. were applied to study the surface relaxation of the nonhydroxylated, hydroxylated, and solvated surfaces of α-Fe2O3 (hematite). We find that our nonhydroxylated structures and energies are in good agreement with previous LDA calculations on α-alumina by Manassidis et al. [Surf. Sci. Lett. 285, L517, 1993]. Using the results of molecular dynamics simulations of solvated interfaces, we define end-member hydroxylated-hydrated states for the surfaces which are used in energy minimization calculations. We find that hydration has a small effect on the surface structure, but that hydroxylation has a significant effect. Our calculations, both for gas-phase and solutionphase adsorption, predict a greater amount of hydroxylation for the α-Fe2O3 (012) surface than for the (001) surface. Our simulations also indicate the presence of four-fold coordinated iron ions on the (001) surface.
A tight-binding total-energy model parametrized to first-principles linearized augmented plane-wa... more A tight-binding total-energy model parametrized to first-principles linearized augmented plane-wave computations is applied to study elasticity and elastic anisotropy in Fe, Xe, and Si at high pressures. We find that the model works well in reproducing the compression, electronic structure, phase relations, and elasticity in these diverse materials. In Xe, for example, the same parametrization works well over a fivefold compression range from a van der Waals solid to a dense metal. We find that the cubic close-packed structures are all more anisotropic than hexagonal close packed and that at high pressures the elastic anisotropy approaches that of any central force nearest-neighbor model. We find that long-range, nonorthogonal parametrizations are necessary for greatest accuracy. ͓S0163-1829͑97͒04738-3͔